Dr. Mohsen Safaei Profile

Dr. Mohsen Safaei

Research Assistant at Tennessee Technological Univ.

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Publications (6)

Proceedings Article | 1 April 2019 Presentation + Paper

Finite element evaluation of EMI-based structural health monitoring in high frequencies

Mohsen Safaei, Eric Nolan, Steven Anton

Proceedings Volume 10972, 109720C (2019) https://doi.org/10.1117/12.2514336

KEYWORDS: Ferroelectric materials, 3D modeling, Structural health monitoring, Aluminum, Data modeling, Electromagnetic coupling, Algorithm development, Optimization (mathematics), Electrodes, Sensors

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Proceedings Article | 27 March 2019 Presentation + Paper

Feasibility of force detection in 3D printed flexible material using embedded sensors

Robert Ponder, Heather Roberts, Mohsen Safaei, Steven Anton

Proceedings Volume 10970, 109702F (2019) https://doi.org/10.1117/12.2514051

KEYWORDS: Sensors, Piezoresistive sensors, Resistance, Resistors, Calibration, Computer aided design, Gait analysis, 3D modeling, Data modeling, Data acquisition

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Proceedings Article | 15 March 2018 Paper

Detection of compartmental forces and location of contact areas with piezoelectric transducers in total knee arthroplasty

Mohsen Safaei, Robert Ponder, Steven Anton

Proceedings Volume 10595, 105951Q (2018) https://doi.org/10.1117/12.2296250

KEYWORDS: Transducers, Sensors, Ferroelectric materials, Surgery, Prototyping, Signal generators, In vivo imaging, Signal processing, MATLAB, Data acquisition

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Total knee arthroplasty, as one of the most common surgeries in the United States, has been widely used to help restore the functionality of damaged knee joints. Alignment of the knee joint during surgery is an extremely important factor to achieve a successful operation. Several methods have been used to quantify the alignment and to provide surgeons with a repeatable method of surgery. However, lack of in vivo information has hindered establishment of correlation between intra- and postoperative knee conditions. In this work, the application of multiple piezoelectric transducers encapsulated inside the ultra high molecular weight polyethylene knee bearing for collecting in vivo data is suggested. The piezoelectric elements display the ability to sense and harvest energy from the joint during daily activity. As a sensor, piezoelectric transducers are designed to measure the compartmental forces as well as the location of the contact points between the femoral and tibial components of the knee implant. Initially, finite element analysis is performed to investigate the sensing performance of the system. In addition, a prototype instrumented bearing is fabricated and the performance of the system in measuring the forces and locations is investigated experimentally. In the experiments, the voltage signals generated by the piezoelectrics are obtained and processed to measure two components of force as well as two different contact points, one each on the medial and lateral compartments of the knee bearing. On the other hand, the actual force profile and the location of contact areas are recorded using the load frame’s built in load cell, and pressure-sensitive films, respectively, and compared to the measured data from the piezoelectrics. The result of FE simulation showed a maximum error of about 1.5% in force sensing and a maximum deviation of about 0.5 mm in the measured location of the contact points. The experimental results also showed that the measured force and location by the piezoelectric sensors match the actual quantities measured from load frame and pressure film fairly well.

Proceedings Article | 10 April 2017 Presentation + Paper

Analytical and finite element performance evaluation of embedded piezoelectric sensors in polyethylene

Mohsen Safaei, Steven Anton

Proceedings Volume 10172, 101720I (2017) https://doi.org/10.1117/12.2260347

KEYWORDS: Transducers, Sensors, Structural health monitoring, Error analysis, Systems modeling, Smart materials, Biopolymers, Data acquisition, Embedded systems, Ferroelectric materials, Dielectrics, Numerical analysis, Finite element methods, Electroluminescence

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A common application of piezoelectric transducers is to obtain operational data from working structures and dynamic components. Collected data can then be used to evaluate dynamic characterization of the system, perform structural health monitoring, or implement various other assessments. In some applications, piezoelectric transducers are bonded inside the host structure to satisfy system requirements; for example, piezoelectric transducers can be embedded inside the biopolymers of total joint replacements to evaluate the functionality of the artificial joint. The interactions between the piezoelectric device (inhomogeneity) and the surrounding polymer matrix determine the mechanical behavior of the matrix and the electromechanical behavior of the sensor. In this work, an analytical approach is employed to evaluate the electromechanical performance of 2-D plane strain piezoelectric elements of both circular and rectangular-shape inhomogeneities. These piezoelectric elements are embedded inside medical grade ultra-high molecular weight (UHMW) polyethylene, a material commonly used for bearing surfaces of joint replacements, such as total knee replacements (TKRs). Using the famous Eshelby inhomogeneity solution, the stress and electric field inside the circular (elliptical) inhomogeneity is obtained by decoupling the solution into purely elastic and dielectric systems of equations. For rectangular (non-elliptical) inhomogeneities, an approximation method based on the boundary integral function is utilized and the same decoupling method is employed. In order to validate the analytical result, a finite element analysis is performed for both the circular and rectangular inhomogeneities and the error for each case is calculated. For elliptical geometry, the error is less than 1% for stress and electric fields inside and outside the piezoelectric inhomogeneity, whereas, the error for non-elliptical geometry is obtained as 11% and 7% for stress and electric field inside the inhomogeneity, respectively.

Proceedings Article | 5 April 2017 Presentation + Paper

Design, analysis, and fabrication of a piezoelectric force plate

Elias Hoummadi, Mohsen Safaei, Steven Anton

Proceedings Volume 10170, 101700W (2017) https://doi.org/10.1117/12.2260381

KEYWORDS: Surgery, Finite element methods, Sensors, Data acquisition, Error analysis, Piezoresistive sensors, Biomedical engineering, Ferroelectric materials, Ceramics, 3D printing, Performance modeling, Prototyping, Capacitance, Printing

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Force plates are used to detect static and dynamic reaction forces due to presence of stationary or moving objects as well as the location of applied forces. The application of force plates in various biomechanical fields, such as gait analysis, has been widely suggested and investigated in the past. Several sensor technologies like piezoelectrics, capacitance gauges, and piezoresistive sensors are utilized to develop force plates with special characteristics. Among the technologies employed in force plate designs, piezoelectrics present the ability of providing a self-powered sensory system. Recently, it has been suggested to implement piezoelectric transducers as sensors in the tibial bearing of total knee replacement (TKR) implants in order to transform the knee bearing into a force plate with the ability to detect force and contact point location for in vivo knee load analysis. Considering this application, a simplified design of a force plate instrumented with six piezoelectric transducers is presented in this study. The force plate is modeled using a finite element (FE) model to investigate the sensing performance of the system. In order to validate the simulation, a prototype force plate is fabricated and tested under the same loading condition applied on the FE model. The results are presented in terms of measured location and amplitude of applied force measured by the piezoelectric transducers. For the FE simulation, the deviation of the measured location of the applied force from the actual location is obtained as 0.62 mm in the x-direction and 0.13 mm in the y-direction, and the error in the amplitude of the measured force is 0.03% of the applied force. On the other hand, the deviation in the measured location of the force from the experimental test is 0.53 mm in the x-direction and 0.1 mm in the y-direction, while the error in force is 3.6% of the applied force. The small quantities of error in both sensed location and amplitude of applied force obtained from the FE simulation and experimental test results demonstrates the potential of the proposed design to be utilized as the sensor in the knee bearing of TKR implants.

Proceedings Article | 15 April 2016 Paper

The effects of dimensional parameters on sensing and energy harvesting of an embedded PZT in a total knee replacement

Mohsen Safaei, Steven Anton

Proceedings Volume 9799, 97992P (2016) https://doi.org/10.1117/12.2219462

KEYWORDS: Energy harvesting, Ferroelectric materials, Transducers, Sensors, Data modeling, Surgery, Systems modeling, Gait analysis, Finite element methods, In vivo imaging, Data acquisition, Magnetic sensors

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